Antigen Recognition by Variable Lymphocyte Receptors (VLR) in the Sea Lamprey

两种类型的重组适应性免疫系统出现在大约5亿年前脊椎动物辐射的黎明。下颚脊椎动物通过免疫球蛋白（Ig）基因片段的V(D)J重排产生多种B细胞和T细胞抗原受体。与此形成鲜明对比的是，像海七鳃鳗这样的无颌脊椎动物，通过重组插入不同的富含亮氨酸的重复序列（LRR）模块单元，将它们的可变淋巴细胞受体（VLR）从侧翼的卡带中组装到种系VLR基因中。抗原库的组合多样性约为1014种独特的抗原受体，适用于LRR和基于igg的适应性免疫系统。考虑到无颌和有颌脊椎动物是寒武纪幸存下来的仅有的两个脊椎动物分类群，这一点很有趣。进化出不是一种而是两种不同类型的重排淋巴细胞抗原受体的选择压力是什么？VLRs和抗体的进化是偶然和必要的，以识别抗原世界的相似或可能不同的决定因素吗？本项目将探讨VLRs在七鳃鳗免疫中的作用。通过VLR的抗原识别将在各种抗原免疫刺激的动物中进行研究，包括外源蛋白、微生物细胞壁成分、微生物DNA和RNA。利用免疫动物淋巴细胞构建VLRs文库，筛选特异性高的抗原结合受体。选定的VLR结合其同源配体，然后结晶，以确定配合物的三维结构，并确定VLR与其配体之间的接触残基。VLR的功能和结构特征可能有助于阐明适应性免疫的起源，特别是因为LRR模块也是我们自己的主要先天微生物检测受体的基石，如toll样受体和细胞质NBS-LRR家族成员，以及植物中含有LRR的抗病基因。这个项目将包括对几名不同学术背景的学生进行培训。此外，Pancer博士将把他的研究成果纳入比较和进化免疫生物学的教学课程。

Two types of recombinatorial adaptive immune systems appeared at the dawn of vertebrate radiation ~500 million years ago. Jawed vertebrates generate a diverse repertoire of B and T cell antigen receptors through V(D)J rearrangement of immunoglobulin (Ig) gene fragments. In sharp contrast, jawless vertebrates such as the sea lamprey, assemble their variable lymphocyte receptors (VLR) through recombinatorial insertion of diverse leucine-rich repeat (LRR) modular units, from flanking cassettes into the germline VLR gene. The combinatorial diversity of the repertoire is about 1014 unique antigen receptors, both for the LRR and the Ig-based adaptive immune systems. This is intriguing when considering that jawless and jawed vertebrates are the only two vertebrate taxons that survived from the Cambrian period. What was the selective pressure to evolve not one but two different types of rearranging lymphocyte antigen receptors? Did VLRs and antibodies evolve by chance and necessity to recognize similar, or perhaps different determinants of the antigenic world? The role of VLRs in lamprey immunity will be explored in this project. Antigen recognition by VLR will be studied in animals immunostimulated with various types of antigens, including foreign proteins, microbial cell wall components, and microbial DNA and RNA. Libraries of VLRs will be constructed from lymphocytes of immunized animals, to select those receptors that can bind the antigens with high specificity. Selected VLRs bound to their cognate ligand will then be crystallized, to determine the three-dimensional structure of the complexes, and to identify contact residues between the VLR and its ligand. Functional and structural characterization of the VLR may help elucidate the origin of adaptive immunity, in particular since LRR modules are also the building blocks of our own cardinal innate microbial detection receptors, such as the Toll-like receptors and the cytoplasmic NBS-LRR family members, and the LRR-containing Disease Resistance genes of plants. This project will involve the training of several students at varying academic backgrounds. In addition, Dr. Pancer will incorporate his research results in teaching a course in comparative and evolutionary immunobiology.